Morphological evolution of TiC particles with different stoichiometries by hydrofluoric acid etching treatment

Abstract

The effects of hydrofluoric acid (HF) etching time on the morphology of the titanium carbide (TiC) particles with different stoichiometries were investigated. TiC particles with two C/Ti molar ratios of 0.5 and 1.0 were prepared by mechanical alloying.Then, the powders were immersed in the HF solution for different times of 48, 96, and 142 h. Results showed that the morphology of TiC particles greatly changed after HF etching. In general, a roughing phenomenon was observed as a function of the immersion time in the HF solution. The irregular shape of the TiC particles changed to the spherical shapes by increasing the HF etching time. However, the changing tendency of TiC particles with different stoichiometries was different. The shape of prepared powders with a C/Ti molar ratio of 1.0 was polyhedron at the initial stages of HF treatment, while the shape of prepared powders with a C/Ti molar ratio of 0.5 was near-spherical. However, with increasing the immersion time, the shape of both samples changed to a spherical one. The degree of roughing phenomenon of the prepared powders with a C/Ti molar ratio of 0.5 was lower than that of the prepared powders with a C/Ti molar ratio of 1.0.

Evaluation of zirconia surfaces and shear bond strength after acid–etching with ultrasonic vibration

“…The acid etching possesses the advantage of homogenous roughening of the material regardless of its size and shape. In addition, this method exhibits no risk of material delamination as it does not exert stress on the material [19,20]. Therefore, more studies should be performed to create microretention to improve the efficacy of surface treatment methods for zirconia, particularly with the use of stronger acids.…”

“…As the etching time prolonging, the spicules appeared and continued to increase, while the octahedrons seemingly to be gradually cover-ed so that the number of octahedrons on the surface was evidently reduced at 60 min (figure 2). Heidarpour Akbar et al indicate that the stoichiometry of reactants and the kinetic roughing mechanism with increasing the HF etching time leading to the occurrence of shape evolution [20,27]. According to the EDS analysis, these spicules were composed of F and Zr, whose atomic percentage was approximately to 1:4.…”

“…Therefore, the size and distribution of pores on the sample surface cannot be fully explained through the simple roughness measurement, so the porosity and total pore area, should be evaluated in future research, not just the roughness [32]. In addition, due to the surface adsorption of fluoride ions, the surface energy has decreased by increasing the immersion time, which may also be responsible for the decrease in bond strength after longer etching [20]. The shear stress of samples in Group P was higher than that in Group C, remaining higher after cooling-heating cycles, indicating that the octahedrons formed enhanced the surface roughness and improved the zirconium-resin bonding force.…”